Healer DPS is nice and all, but I've never thought of a healer as lazy if they didn't DPS. I've thought of a healer as lazy if they're slow with heals. I don't particularly care if the heal was slow because they were trying to both DPS and heal, it's still lazy because their primary role is healing, not damage, and that's the part they were slacking on. It's about the vigilance required to monitor HP bars and think about the incoming damage.